The spelling of the word "one for bird" can be explained using the International Phonetic Alphabet (IPA). The first sound in "one" is the vowel sound /ʌ/, which is pronounced with an open, relaxed mouth. The second sound in "for" is the vowel sound /ɔː/, which is a longer, more rounded version of the sound in "hot." Finally, the word "bird" is pronounced with the consonant sounds /b/ and /d/ and the vowel sound /ɜː/, which is similar to the sound in "herd." Together, these sounds make up the unique spelling of "one for bird."